Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$129.62	12.691%	$146.0701	$146.07	$146.05	$146.10
Purchase #2	$147.53	12.112%	$165.3988	$165.40	$165.40	$165.40
Purchase #3	$58.85	11.373%	$65.543	$65.54	$65.55	$65.50
Purchase #4	$123.90	3.664%	$128.4397	$128.44	$128.45	$128.40
Purchase #5	$82.97	9.172%	$90.58	$90.58	$90.60	$90.60
Purchase #6	$99.39	12.106%	$111.4222	$111.42	$111.40	$111.40
Purchase #7	$77.39	11.712%	$86.4539	$86.45	$86.45	$86.50
7 purchase totals =	$719.65		$793.9077	$793.90	$793.90	$793.90